Combustion method



Y L. F. CONWAY COMBUSTION- METHOD Oct. 17, 1944;

2 Sheets-Sheet 2 riginal Filed Dec. 27. 1940 00 mvEN-roR D Leon -Comvay IIII IILHLI MNC.

Patentedl ct. 17, 1944 COMBUSTIGN' METHDD Leon F. Conway, Pittsburgh. Pa.. assignor to Frederick S. Bloom, Pittsburgh, Pa.

Original application December 27, 1940, Serial No. 1 371,862. ADivided and this application February 5, 1942. Serial No. 429,643

4 claims. (ci. 15a-117.5)

u This invention relatesto the combustion of fluid fuel, and, particularly, to a method for' producing the combustion of hydrocarbon gas such as natural gas with a luminous flame.

This is a division from my application Serial No. 371,862 led December 27, 1940, forCombustion apparatus and method..

Lminous-iiame burners 'have beenv known heretofore but have been characterized by' a limited thermal capacity'compared to burners producing a non-luminous or clear flame. generally accepted 'that the production of a luminous flame necessitates cracking of the carbon from hydrocarbon fuel by a slow burning process so that the heat generated by the combustion which occurs initially cracks at least a portion of the remaining hydrocarbon fuel producing hydrogen and atomic carbon whichv lines at equal low velocities so that they mix slowly over the areaof contact of the two streams and combustion starts in that area. Known types of luminousflame burners, however, have been limited in their application to large furnaces in which the amount of heat liberated per cubic foot of furnace volume is-relatively low, i. e., less than 35,000 B. t. u. per hour.

I have invented-a novel method and apparatus for the combustion of hydrocarbonfuel with a luminous ame, adaptable to furnaces requiring a heat input in excess of the figure above men- I tioned, e. g., up to 70,000 B. t. u. per hour per cubic foot of combustion space#y ,In a preferred practice of the invention, I discharge a fuel jet substantially centrally of an annular air stream and The apparatus for producing combustion according to my method may take various forms and is claimed in my copending application-identifled above. In its simplest form, the apparatus may comprise a fuel tube having va wall thickness such that an annular stream of air iiowing past the end thereof creates a partial-vacuum condition adjacent the end. This causes the outer Itis.

layer of fuel to be pulled outwardly and the inner layer of air to be drawn inwardly, without materially affecting the remaining portions of the fuel and air streams. tube may have a thickened end portion tapering rearwardly to increase the velocity of the air as it sweeps around the' end of the fuel tube.- In a further form, an annular baille is mounted on the fuel tube adjacent the discharge end.

Further novel features and advantages of the invention will become apparent during the following detailed description of the apparatus and method briefly outlined above, with reference to the accompanying drawings illustrating the method diagrammatically and showing a preferred embodiment of the apparatus and certain impart only suicient turbulence to the adjacent layers of vfuel and air near the plane of their initial contact to cause rapid mixing of such layers without materially affecting the central core of the fuel stream or the outer layers of thel air stream'. 'I'he air is introduced at a velocityhigher than that of the gas and the condition of turbulence at the zone of initial contact may conveniently be obtained by creating a low-pressure rapid mixing of the adJacent layers of fuel and air creates an Vannular column of combustion gases, the heat from which cracks the remaining fuel, releasing the carbon to produce a luminous name. The cracked fuel and the remaining air are then mixed .gradually on continued flow and vcombustion 'spreads quickly over the entire section of the stream of air and fuelm'ixture,

modifications., In the drawings,

Figure 1 is a'diagrammatic view illustrating the flow of fuel and air which I produce in order to obtain combustion with a luminous flame ofhigh thermal capacity, and the simplest form of apparatus for achieving this mode of operation;`

vanother form of apparatus;

Figure 4 Iis a similar View' showing a further modification;

Figure 5 is acentral vertical longitudinal section through a complete burner embodying the v principles of my invention; and

. or partial-vacuum condition in said zone. The

cated atIZ, e. g., through the wall Figure 6 is a vtransverse sectional view taken substantiauy'amng the plane of line rrr-V1 of Figure 5. t

Referring now in detail to the drawings and,

for the present, to Figures 1 and 2, I have there lillustrated a stream of hydrocarbon fuel l0 being discharged substantially centrally of an annular air stream ll. Throughout the drawings the air.

The Vair stream Il may b e conceived of as flowing along any suitable duct or In another form, the fuel light. arrows indicate fuel and the heavy arrows passage indiofa furnace,

toward a combustion space therein indicated generally at I3. The fuel stream I flows through a nozzle or supply tube I4. I maintain a pressure on the air supply such that the Velocity of the air as it sweeps around the end of the tube I'4 is somewhat greater than the velocity of the fuel flowing through the tube I4. As illustrated, the radial thickness of the air stream is only slightly less than the diameter of the fuel stream. In other words, the fuel stream has a diameter less than one-half the outside diameter of the air stream.

The tube I4 has a wall thickness such that a condition of partial vacuum or low pressure is created in anannular zone.- I5 adjacent the end of the tube. This condition of low pressure causes the outer layer of the fuel stream to be pulled outwardly and the inner layer of the air stream to be drawn inwardly, as indicated by the arrows in Figure 1, without materially affecting the central core of the fuel stream or the outer layers of the air stream. This condition is also illustrated in Figure 2 where I have adoptedthe conventional symbol, i. e., a cross, indicating the tail of an ongoing arrow to indicate flow toward and through the plane of the paper. As clearly shown in Figure 2, the heads of the arrows in the outer layer of the fuel stream I8 are deflected outwardly, and the heads of the inner arrows of the air stream are deflected inwardly.

, The above described diversion of portions of the fuel and air streams results in rapid mixing of these portions in the zone I5 adjacent the point of initial contact, i. e.,`the end of the tube I4. This partial mixture of the fuel and air causes combustion to be initiated in an annular column, as indicated by the dotted arrows, commencingclose to the zone I5, assuming previous.`

ignition of the ongoing stream of fuel and air at a point somewhere in the' combustion space I3. The exact point at which combustion begins depends, vof course, on the relative proportions of fuel and air, the velocity of the two streams and other conditions with which those skilled in the art are well acquainted.` This initial combustion furnishes sufficient heat to crack the fuel in the central core of the stream I0, releasing carbon which imparts a high degree of luminosity to the flame. Thereafter, the remainder of the fuel becomes mixed with the remainder of 'Ihe thickened end 20 of the tube I9 produces an even more marked condition of low pressure or partial vacuum at the point of initial contact between the air and fuel than the fuel tube I4 of Figure l. An even more rapid mixing of the inner layer of air and the outer layer of fuel is thereby effected with the initiation of combustion in an annular column as illustrated by the dotted arrows. It will be evident that the apparatus shown in Figure 3 operates on precisely the same principle as explained with reference to Figures l and 2, the only difference being that already pointed out.

Figure 4 illustrates a further modification in which a kfuel tube 22 extends coaxially into an ner layers of the air stream flowing through the pipe 23. As a matter of fact, the turbulence resuits from a partial-vacuum or low-pressure condition just beyond the baille. It is evident, therefore, that'the structure shown in Figure 4 will be effective to produce combustion according to my method which has already been fully explained with reference to Figures l and 2.

Referring now more particularly to Figures 5 and 6, I have there shown a complete burner indicated generally at 25 associated with a port block 26 which may be assumed to form part of a furnace wall 21.- The burner 25 comprises generally an air chamber 28 having a flange 29 on one side thereof projecting into the port formed the air and combustion spreads inwardly and` outwardly from the aforesaid annular column until it is substantially continuous over the entire section of the ongoing stream of mixed fuel and air, or throughout the combustion space I3.

Referring now to Figure 3 showing am embodiment of the invention as applied to a. furnace burner, a port block -IS has a flaring throat I1 opening into a combustion chamber which may be the interior of a furnace or other space to be heated. An air .pipe or duct I8 extends into the opening-through the port block from the exterior thereof and is connected by any suitable means to a convenient source of air under appropriate pressure. 'A fuel'tube or nozzle I9 extends through the air pipe I6 substantially centrally thereof and is connected to a suitable source of hydrocarbon fuel. The wall of the tube I9 is 'thickened adjacent the discharge end as indicated at 28 and decreases in thickness away from the extreme endrearwardly thereof. This construction provides an annular Venturi throat 2i which increases the velocity of the air flowing through the pipe I8 as it passes the extreme end of the tube I8.

chamber to the frusto-conical wall 32 and a cup shaped casting 36 secured to the rear wall of the air chamber. The casting 38 has a hole 31 therein tapped to receive a fuel pipe 38. A fuel tube 38 is slidable through an opening in a wall 48 extending inwardly from the annular wall 35 and the frusto-conical wall 32. An adjusting rod 4I extends through the rear wall of the casting 38 having a gland 42 therein. 'I'he outer end of the rod has a knob 43 thereon while the inner en d is secured to a spider 44 in the inner end` l of the tube 39. The tube 38 is provided with an annular baille 45 secured thereto adjacent the discharge end thereof. The rear outer edge of the baille is beveled as at 48.

With the fuel tube 39 in the position illustrated insolid lines it will be apparent that air supplied to the chamber 28 through the pipe 38 will flow yinto theport in the block 28 through the holes 33 and be distributed uniformly overthe annular area of the section of theA port between the tube 39 andthe block. Fuel supplied through the pipe 38 flows into the chamber 34 and the tube 38 and is thereby introduced centrally of the annular air stream. `The baille V45 creates the condition It will be of turbulence in the inner lays of the air stream caused by the partial vacuum or low pressure condition beyond the baille which results in partial mixing of the fuel and air adjacent their point of initial contact in the manner already explained. This initial combustion cracks at least a portion of the remaining fuel and thereby imparts a high degree of luminosity to the flame.

. The remainder .of the fuel and air become rapidly mixed and combustion proceeds to completion.

If combustion with a clear non-luminous flame is desired, it is only necessary to pull back on the knob 43. When the tube 39 and baille 45 are in the positions indicated in chain lines, the baille does not affect the flow of the air stream. Instead of an annular stream of aircoaxial with the port in the block 2B, the holes 33 create a plurality of air jets directed inwardly into a central fuel stream issuing from the tube 39. The angularity of the air jets relative to the fuel stream causes immediate mixture of all the gas and air so that rapid combustion with a clear flame ensues.

It will be apparent from the foregoing description and explanation that the invention is characterized by numerous advantages over combustion methodsknown heretofore. In the rst place, the burner of my invention permits the production of a luminous flame with higher fuel and air velocities than ave been possible heretofore whereby I am a le to obtain a greater heat input per minute per cubic foot of combustion space. This is possible because I effect quick mixing of a portion of the fuel and air for combustion to effect the cracking of the remainder of the fuel. This is accomplished by producing the turbulence which results from the lowpressure or partial-vacuum condition created adjacent the point of initial contact between the fuel' and air. After the initial combustion and cracking, the remaining fuel and air mix rapidly because the turbulence at the point of initial contact carries over into the latter stages of combustion, so that combustion proceeds to completion with a highly luminous flame. method and apparatus disclosed, it is possible to obtaina heat liberation per cubic foot of combustion space oi' about 70,000 B t. u. per hour which is comparable to that obtained with conventional non-luminous burners.

Although I have illustrated and described but a preferred practice and certainvariations of the method of my invention it will be understood that changes may be made inthe procedure disclosed without departing from the spirit of the invention or the scope of the appended claims.

1. In a method of producing a luminousfiame,

By the the steps including supplying an annular air stream in which the air is substantially uniformly distributed over the sectional area of the stream, discharging a gaseous fuel jet substantially centrally of the air stream, at a velocity lower than thatof the latter, and generally parallel thereto, creating a partial vacuum around the zone of contact between fuel and air at the point Where they initially come in ',contact, and thereby producing turbulence in the adjacent layers only of fuel and air and causing rapid partial mixing thereof so that combustion of the mixed portions of fuel and air, on ignition thereof, furnishes sufiicient heat to crack the remaining fuel and produce a luminous 'flame on complete combustion thereof.

2.' In a method of producing a luminous flame,

the steps including supplying a stream of air under pressure. supplying a jet of gaseous hydrocarbon fuel adjacent the center of the stream of air, defiecting the inner layer of the air stream outwardly adjacent the point 0f initial contact thereof with the fuel, to produce turbulence in only the adjacent layers of fuel and air and cause rapid mixingof said layers only thereof adjacent said point, whereby ignition of the mixed fuel and air results in partial combustion and release of carbon, followed by complete combustion with a luminous flame on gradual mixture of the remainder of the fuel -with the remainder of the air.

3. In a method of producing a luminous flame, the steps including supplying a streamvof air under pressure supplying a jet of gaseous hydrocarbon fuel adjacent the center of the stream of air, accelerating the air stream adjacent the point of initial contact thereof with the fuel, producing turbulence of the contacting layers only of air and fuel adjacent said point, thereby causing rapid mixing thereof so 'that ignition of said mixed fuel and air results in partial combustion and release of carbon, followed by complete combustion withl a luminous flame on gradual mixture of the remainder of the fuel with the remainder of the air.

4. In a method of producing a luminous flame,

crack the remaining fuel and produce a lumi-` nous ame on complete combustion thereof.

LEON F. CONWAY. 

